DE 195 42 551 A1 discloses a linear motor having a hollow-cylindrical primary part, which has annular primary coils which are arranged concentrically with respect to a movement axis of a secondary part and can be operated with polyphase current. Annular laminates composed of soft-magnetic material are arranged between the primary coils, are used as intermediate elements to separate adjacent primary coils, and form magnetizable teeth, in order to amplify the magnetic flux and to pass this to the receptacle in which the secondary part is arranged. The primary coils and the annular laminates are accommodated in a hollow-cylindrical yoke composed of magnetizable material, which forms a magnetic return path. The secondary part is arranged such that it can move axially within the receptacle that is formed by the primary part. The secondary part has a plurality of field magnets composed of superconductor windings, which are arranged one behind the other with alternating polarity in the axial direction. In DE 195 42 551, the magnetic fields of the secondary windings are at right angles to the axis of the secondary part. In order to produce this field direction using wound coils, the axis of each individual coil through which current flows must be at right angles to the movement axis of the linear motor. Only if permanent magnets or superconducting solid-body magnets are used can these magnets rest with their inner circumferential surface on a cylindrical yoke composed of magnetizable material. Although these then have an annular shape, they are magnetized radially, however. In the case of wound secondary coils, in contrast, an arrangement must be chosen in which the wound coils are offset alongside one another in the circumferential direction and in the axial direction on the casing surface of the supporting body. The magnetic forces which are produced when current is applied to the primary and secondary coils produce a relative movement between the primary part and the secondary part.
EP 1 465 328 A1 discloses a linear motor in which the primary part and secondary part are arranged reversed, such that the secondary part is on the outside, and surrounds the primary part.
The capability to magnetize the soft-magnetic teeth is restricted because magnetic saturation occurs in the soft-magnetic material. In order to achieve higher force densities between the primary part and secondary part with high current densities in the coils of the primary part, it has been proposed that the number of turns in the primary coils be increased or that the amount of magnetizable material be increased. These measures have allowed force densities of up to about 8 N/cm2 to be achieved in the trials stage for round and polysolenoid linear motors. However, the physical size and the weight of the linear motors have to be significantly increased to do this.